Electric utilities frequently log ambient temperature as a part of their electric usage surveys. The primary purpose of such logging is to measure the ambient temperature associated with a particular electric meter or data recorder. These surveys are used to determine the power usage at a given site, for example a residence or commercial office, so as to allow correlation of power usage with outside temperature. This provides the utilities with an idea as to how much power it takes to run air conditioners or electrical heaters, both which are known heavy electrical power users.
Presently available devices for measuring temperature typically convert temperature to pulses for a survey recorder, such as a KYZ data pulse recorder. Prior art approaches require a source of external power, and typically also require a connection to an external temperature sensing element such as a thermocouple.
In one prior art device, eight different terminals are required for connection of the temperature monitor to the data recorder. These terminals include: two terminals for receiving 110 volts AC for system power, two terminals for providing the pulse output, a terminal for safety-grounding the device, and three terminals for connecting an external temperature probe. Needless to say, the provision of a plurality of terminals complicates the usage of the device since several electrical connections must be made every time a device is installed or repaired. Moreover, provision must be made for running power cables, signal cables, and probe wires. While such a configuration with a remote temperature probe may be preferred in some applications, for example, if the temperature inside a transformer is to be measured, a more widespread application is in the measurement of ambient temperature for correlation of temperature with power usage. For such applications, additional wire connections and the requirement for an external power supply is impractical and may make the application cost-prohibitive.